

18-1

Conspicuous nucleus
Travel in blood before migrating
to connective tissue
Protect against pathogens
Leukocyte Descriptions
• Granulocytes
– neutrophils (60-70%)
• fine granules in cytoplasm; 3 to 5 lobed nucleus
– eosinophils (2-4%)
• large rosy-orange granules; bilobed nucleus
– basophils (<1%)
• large, abundant, violet granules (obscure a large S-shaped nucleus)
• Agranulocytes
– lymphocytes (25-33%)
• variable amounts of bluish cytoplasm (scanty to abundant);
ovoid/round, uniform dark violet nucleus
– monocytes (3-8%)
• largest WBC; ovoid, kidney-, or horseshoe- shaped nucleus
18-2
Granulocyte Functions
• Neutrophils ( in bacterial infections)
– phagocytosis of bacteria
– release antimicrobial chemicals
• Eosinophils ( in parasitic infections or allergies)
– phagocytosis of antigen-antibody complexes,
allergens and inflammatory chemicals
– release enzymes to destroy parasites
• Basophils ( in chicken pox, sinusitis, diabetes)
– secrete histamine (vasodilator)
– secrete heparin (anticoagulant)
18-3
Agranulocyte Functions
• Lymphocytes ( in diverse infections and
immune responses)
–
–
–
–
destroy cells (cancer, foreign, and virally infected cells)
“present” antigens to activate other immune cells
coordinate actions of other immune cells
secrete antibodies and provide immune memory
• Monocytes ( in viral infections and inflammation)
– differentiate into macrophages
– phagocytize pathogens and debris
– “present” antigens to activate other immune cells
18-4
Complete Blood Count
• Hematocrit
• Hemoglobin concentration
• Total count for RBCs, reticulocytes, WBCs,
and platelets
• Differential WBC count
• RBC size and hemoglobin concentration per
RBC
18-5
Leukocyte Life Cycle
• Leukopoiesis
– pluripotent stem cells – most WBCs develop in the bone
marrow
– T lymphocytes complete development in thymus
• Red bone marrow stores and releases granulocytes and
monocytes
• Circulating WBCs do not stay in bloodstream
– granulocytes leave in 8 hours and live 5 days longer
– monocytes leave in 20 hours, transform into macrophages and
live for several years
– WBCs provide long-term immunity (decades)
18-6
Leukocyte Disorders
• Leukopenia - low WBC count (<5000/L)
– caused by: radiation, poisons, infectious disease
– effects: elevated risk of infection
• Leukocytosis = high WBC count (>10,000/L)
– caused by: infection, allergy and disease
– differential count - distinguishes % of each cell type
• Leukemia = cancer of hemopoietic tissue
– myeloid and lymphoid - uncontrolled WBC production
18-7
Fig. 18.18
18-8
Leukopoiesis